A conventional GSM (Global System for Mobile Communications) or UMTS (Universal Mobile Telecommunications Service) core network uses bearer control and call control. The bearer control is the aspect of signaling related to the control of the selection of a path through the transmission network and utilizing (reserving, releasing and setting up) the required resources. The call control is the aspect of signaling related to the subscriber and service control, taking, e.g., the subscriber state into consideration.
In the existing implementations of N-ISDN (Integrated Services Digital Network) the call control and the bearer control are integral with one another. A user plane is associated directly with the control servers, such as MSCs (Mobile Services switching Centers) and GMSCs (Gateway MSCS). Thus, the control nodes implement both application logic for signaling and the user plane.
The present invention is directed to separation of the call control and the bearer control.
For implementation of GSM and UMTS core networks there is a new approach to separate call control and bearer control.
In accordance with the invention, with the implementation of separation between call and bearer control, the following features are described:
Transfer the MGW address, a termination and possibly the chosen transcoder in a backward direction.
The application software is independent from the used transmission technology, e.g. STM, ATM, IP.
Changes to call control and bearer control signaling to achieve the optimized user plane set up.
Usage of logical points in the MGW to allow different control servers to use one MGW.
Giving an MSC, TSC server the possibility to control several MGWs by allocating one PC per MGW in the control node.
The user plane routing for call setup is optimized significantly.
The user plane routing for supplementary services CFNREA, CFB, CFNRY, CFU is optimized significantly.
The user plane routing for supplementary services CW, HOLD is optimized significantly.
As in the IAM, optionally, a CODEC list can be included, which had been negotiated between the originating MSC1 and a UE1, the terminating MSC2 can negotiate a CODEC with UE2, which it can signal back via the MSC1 to UE1. By that UE1 and UE2 use the same CODEC, which avoids CODECs in the network giving better quality. In the case that CODECs are necessary within the network, e.g., STM (see FIG. 7) CODECs of equal type can be chosen, allowing TFO.
An MGW is chosen by the first control node, which needs to modify the user plane, and not before.
A chosen MGW1 can be linked out, when a later call control server MSC2 chooses a different MGW2 and reports this to the first control server. The first call control server sets up the user plane towards the different MGW2.
Allowing of pooling of conference call devices in MGWs.
Combining different coded speech streams to one MPTY.
Further features and advantages of the invention will be readily apparent from the following specification and the drawings.